Revised estimates of agricultural fire emissions for Punjab, India: bridging gaps in satellite observations using household survey data

In north India, agricultural burning adversely affects local and regional air quality during the post-monsoon (October-November), when meteorology is favorable for smog and haze formation. While the Moderate Resolution Imaging Spectroradiometer (MODIS), aboard NASA's Terra and Aqua satellites, provides nearly a 20-year record of global fire activity, the sensor cannot adequately capture small, short-lasting agricultural fires due to its moderate spatial resolution (1 km) and limited overpasses (daily), as well as increasing haziness over this region. As a case study, we incorporate household survey data to bridge these gaps in MODIS observations over Punjab, India, during the 2003-2018 post-monsoon burning seasons. In our top-down approach to calculate fire emissions, we develop a four-step method to adjust MODIS Fire Radiative Power (FRP) to take into account: (1) additional small fires detected by the Visible Infrared Imaging Radiometer Suite (VIIRS) at 375 m spatial resolution, (2) cloud/haze gaps, (3) partial field burns, and (4) the fire diurnal cycle. Using our adjusted FRP, we estimate on average 7.3 Tg dry matter burned per season − 44 Gg OC, 3.7 Gg BC, 552 Gg CO, and 10.4 Tg CO₂ − consistent with our bottom-up validation using survey burn rates and government crop production statistics in 2016 and 2017. In order to most effectively constrain agricultural fire emissions, we recommend that future efforts to update emissions inventories for Punjab should target uncertainties in the fire diurnal cycle and fuel consumption.